Na2/3My(Fe1/2Mn1/2)1-yO2/C复合纳米纤维的可控制备、性能调控及改性机理研究

P2-type Na2/3Fe1/2Mn1/2O2 is expected to be a kind of very promising cathode material of Na-ion batteries due to its high theoretical specific capacity (260 mAh/g) and energy density (715 Wh/kg). However, the practical application of P2-type Na2/3Fe1/2Mn1/2O2 is mainly hindered by its low ionic conductivity, effects of air sensitive, alkaline impurities, and Jahn-Teller. In this project, we introduce the method of coaxial electrospining-chemisorption to synthesize hollow/porous nanofibers of Na2/3My(Fe1/2Mn1/2)1-yO2/C (M=high potential cations without J-T effect). The air-sensitive effect can be inhibited with high potential cation doping and nanocarbon coating. The remove of the alkaline impurities by water washing is achieved, thus the electrochemical property and processing performance can be improved. The structure stability can be enhanced with cation doping for inhibiting Jahn-Teller effect. Moreover, the ionic conductivity will be enhanced with utilizing the hollow and porous structure of the nanofibers; the rapid cooperative transmission of electrons and sodium ions can be realized by taking advantage of the interwoven nanofibers. Consequently, the composite cathode materials for sodium ion battery are structural stable, stable in air and exhibit excellent electrochemical performance. The study also will clearly show the modification mechanism. These all can provide new ideas for the development and application of the electrode materials for Na-ion batteries.

P2型Na2/3Fe1/2Mn1/2O2因其较高的理论比容量（260mAh/g）和能量密度（715Wh/kg），成为一种非常具有发展前景的钠离子电池正极材料。然而，空气敏感效应、碱性杂质效应、Jahn-Teller效应和较低的离子电导率等问题抑制了其有效应用。本项目通过“同轴静电纺丝－化学吸覆”法合成Na2/3My(Fe1/2Mn1/2)1-yO2/C（M=无J-T效应的高电势阳离子）中空多孔纳米纤维：通过掺杂高电势阳离子和纳米碳包覆共同抑制空气敏感效应；通过水洗除去碱性杂质来提高材料的电化学性能和加工性能；通过阳离子掺杂抑制J-T效应，提高结构稳定性；利用纳米纤维的中空多孔结构提高材料的离子电导率，利用纳米纤维相互交织来实现电子和钠离子的快速协同传输。通过本项目研究，明晰上述改性机理，最终获得结构稳定、空气中稳定且电化学性能优异的钠离子电池复合正极材料，为新型电极材料的开发提供新思路。

P2型Na2/3Fe1/2Mn1/2O2因其较高的理论比容量（260mAh/g）和能量密度（715Wh/kg），是一种非常具有发展前景的钠离子电池正极材料。然而，空气敏感效应、碱性杂质效应、Jahn-Teller效应和较低的离子电导率等问题抑制了其有效应用。本项目采用同轴静电纺丝－化学吸覆法制备Na2/3My(Fe1/2Mn1/2)1-yO2/C（M=无J-T效应的高电势阳离子）中空多孔纳米纤维：通过掺杂高电势阳离子和纳米碳包覆共同抑制空气敏感效应；通过水洗除去碱性杂质来提高材料的电化学性能和加工性能；通过阳离子掺杂抑制J-T效应，提高结构稳定性；利用纳米纤维的中空多孔结构提高材料的离子电导率，利用纳米纤维相互交织来实现电子和钠离子的快速协同传输。通过本项目的研究，明晰了上述改性机理，最终获得了一种结构稳定、空气中稳定且电化学性能优异的钠离子电池复合正极材料，为新型电极材料的开发提供新思路。在本项目实施过程中共发表学术论文18篇，其中SCI检索17篇，有3篇论文入选ESI高被引论文，其中一篇入选ESI热点论文；获授权发明专利7项，申请发明专利6项；培养博士研究生2人，硕士研究生8人。